Grain growth of ZnO in binary ZnO-V₂O₅ ceramics

Grain growth of ZnO during liquid-phase sintering of binary ZnO-V₂O₅ ceramics has been studied for V₂O₅ contents from 0.5 to 4 mol% and sintering from 900°C to 1200°C. The results are discussed and compared with previous studies in terms of the phenomenological kinetic grain growth expression: Gⁿ - G_oⁿ = K_ot exp(-Q/RT). Addition of V₂O₅ is found to decrease the ZnO grain growth exponent, n, as well as the apparent activation energy, Q. The activation analysis also reveals a change in the rate-controlling mechanism for ZnO grain growth. Following a low-V₂O₅-content (≤2 mol%) of nearly constant Q values of about 88 kJ/mol, further V₂O₅ additions cause an increase of the Q value to about 115 kJ/mol. Consistent with accepted models of liquid-phase sintering, it is concluded that the rate-controlling mechanism of ZnO grain growth during liquid-phase sintering in the presence of V₂O₅ changes from one of a phase-boundary reaction at low V₂O₅ levels to one of diffusion through the liquid phase at more than 2 mol% V₂O₅ levels.